CURLOPT\_SSLKEY\_BLOB(3) Library Functions Manual CURLOPT\_SSLKEY\_BLOB(3)

# [NAME](#NAME)

CURLOPT\_SSLKEY\_BLOB - private key for client cert from memory blob

# [SYNOPSIS](#SYNOPSIS)

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLKEY_BLOB,


                          struct curl_blob *blob);
```

# [DESCRIPTION](#DESCRIPTION)

Pass a pointer to a curl\_blob structure, which contains information (pointer and size) for a private key. Compatible with OpenSSL. The format (like "PEM") must be specified with [*CURLOPT\_SSLKEYTYPE(3)*](/man/os/curl/CURLOPT_SSLKEYTYPE.3).

If the blob is initialized with the flags member of struct curl\_blob set to CURL\_BLOB\_COPY, the application does not have to keep the buffer around after setting this.

This option is an alternative to [*CURLOPT\_SSLKEY(3)*](/man/os/curl/CURLOPT_SSLKEY.3) which instead expects a filename as input.

# [DEFAULT](#DEFAULT)

NULL

# [PROTOCOLS](#PROTOCOLS)

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. only

This option works only with the following TLS backends: OpenSSL and wolfSSL

# [EXAMPLE](#EXAMPLE)

```
extern char *certificateData; /* point to cert */
extern size_t filesize; /* size of cert */
extern char *privateKeyData; /* point to key */
extern size_t privateKeySize; /* size of key */
int main(void)
{


  CURL *curl = curl_easy_init();


  if(curl) {


    CURLcode result;


    struct curl_blob blob;


    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");


    blob.data = certificateData;


    blob.len = filesize;


    blob.flags = CURL_BLOB_COPY;


    curl_easy_setopt(curl, CURLOPT_SSLCERT_BLOB, &blob);


    curl_easy_setopt(curl, CURLOPT_SSLCERTTYPE, "PEM");


    blob.data = privateKeyData;


    blob.len = privateKeySize;


    curl_easy_setopt(curl, CURLOPT_SSLKEY_BLOB, &blob);


    curl_easy_setopt(curl, CURLOPT_KEYPASSWD, "s3cret");


    curl_easy_setopt(curl, CURLOPT_SSLKEYTYPE, "PEM");


    result = curl_easy_perform(curl);


    curl_easy_cleanup(curl);


  }
}
```

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.71.0

# [RETURN VALUE](#RETURN_VALUE)

[*curl\_easy\_setopt(3)*](/man/os/curl/curl_easy_setopt.3) returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see [*libcurl-errors(3)*](/man/os/curl/libcurl-errors.3).

# [SEE ALSO](#SEE_ALSO)

[**CURLOPT\_SSLKEY**(3)](/man/os/curl/CURLOPT_SSLKEY.3), [**CURLOPT\_SSLKEYTYPE**(3)](/man/os/curl/CURLOPT_SSLKEYTYPE.3)

2026-09-24 libcurl

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Document: CURLOPT_SSLKEY_BLOB(3) from curl 8.22.0-r3 (Chainguard OS)
Source: https://github.com/curl/curl.git